Column formwork improvements

ABSTRACT

The present disclosure relates to formwork. In a particular form the present disclosure relates to lost column formwork. In one aspect, there is provided a lost column formwork shell portion comprising an elongate body comprising a generally u-shaped cross-section shape comprising a pair of lengthwise extending edges, an inner side and an outer side, and at least one spacer element depending from the inner side of the shell portion and projecting inwardly. In a further aspect, there is provided a lost column formwork shell assembly comprising a pair of shell portions joined along their lengthwise extending edges. In a further aspect, there is provided a lost column formwork assembly a shell assembly, bracing and reinforcement. The lost column formwork assembly ensures that the required axis distance is maintained across its length, is braced against bulging under the hydrostatic pressure of concrete filling, and is quicker and easier to assemble than commonly known alternatives.

PRIORITY DOCUMENTS

The present application claims priority from Australian Provisional Patent Application No. 2019903147 titled “COLUMN FORMWORK IMPROVEMENTS” and filed on 28 Aug. 2019, the content of which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to formwork. In a particular form the present disclosure relates to lost column formwork.

BACKGROUND

Structural concrete columns are formed by pouring the concrete into shape providing formwork arranged around structural steel reinforcement framework so that the concrete sets around the reinforcement framework.

Lost formwork is formwork which remains in situ after pouring, becoming part of the completed structure. Use of lost formwork permits preassembly of the formwork offsite, reducing delays associated with the set-up, removal and cleaning of conventional reusable formwork.

Lost column formwork comprises a shell into which the structural steel reinforcement framework is positioned and the concrete is poured, and which will remain a part of the completed column.

Fire resistance is a critically important part of structural design of structures. Standards for structural fire design of concrete structures typically require specified minimum dimensions of a cross-sectional area for the structure, and specified minimal distances of reinforcement bar from the surface of the concrete member, the latter being commonly referred to as ‘axis distance’.

A significant issue with lost column formwork relates to preventing bulging or ballooning of a shell of the formwork resulting from hydrostatic pressure once this is filled with concrete.

A further issue is ensuring that the ‘axis distance’ of the reinforcement bar from the surface of the column is properly established during manufacture, and that this axis distance will be maintained when transporting the formwork to the building site, and finally once this formwork is filled with concrete. Where bulging occurs, this axis distance will be greater than required, but insufficient in other (higher) regions on the column. As a result, such a column would not meet the necessary standards.

Yet a further issue is that the long and slender geometry of columns creates difficulties with internal assembly of the lost column formwork, particularly in the central region of the formwork, as this cannot be accessed from the ends thereof.

It is against this background and the problems and difficulties associated therewith that the present invention has been developed.

Certain objects and advantages of the present invention will become apparent from the following description, taken in connection with the accompanying drawings, wherein, by way of illustration and example, an embodiment of the present invention is disclosed.

SUMMARY

According to a first aspect there is provided a lost column formwork assembly comprising:

-   -   a. a first shell portion and a second shell portion, each shell         portion comprises an elongate body comprising a pair of         lengthwise extending edges, and an inner side and an outer side,         wherein at least a first shell portion comprises a generally         u-shaped cross-section, and the shell portions are adapted to         cooperatively form a column shell by being joined along their         lengthwise extending edges;     -   b. each shell portion further comprising at least one spacer         element depending from an inner side of each shell portion and         projecting inwardly;     -   c. and wherein at least the second shell portion comprises an         aperture extending therethrough between the inner side and the         outer side thereof, via which the spacer element for this         portion can be secured thereto;     -   d. the lost formwork assembly further comprising:     -   e. at least one brace element of sufficient length to bridge         opposing inner sides of the two shell portions; and     -   f. a column reinforcement framework; and     -   g. wherein the two shell portions are joined along their         lengthwise extending edges to form a column shell, with the         column reinforcement framework extending lengthwise through the         shell and separated from the shell by the spacing elements, and         with the or each bracing element extending through the         reinforcement framework and between opposing inner sides of the         two shell portions, and secured at opposing ends thereof with         respect to the inner sides of the two shell portions.

In one form, each shell portion comprises an elongate body comprising a generally u-shaped cross-section shape comprising a pair of lengthwise extending edges, and an inner side and an outer side, and adapted to cooperatively form a column shell by being joined along their lengthwise extending edges.

In one form, in an alternative, the second shell portion is substantially flat.

In one form, the lost column formwork assembly further comprises a plurality of the brace elements arranged in parallel, extending transversely across the shell and spaced apart lengthwise therealong.

In a further aspect there is provided a method for assembling a lost column formwork assembly comprising:

-   -   a. a first shell portion and a second shell portion, each shell         portion comprises an elongate body comprising a pair of         lengthwise extending edges, and an inner side and an outer side,         wherein at least a first shell portion comprises a generally         u-shaped cross-section, and the shell portions are adapted to         cooperatively form a column shell by being joined along their         lengthwise extending edges;     -   b. each shell portion further comprising at least one spacer         element depending from an inner side of each shell portion and         projecting inwardly;     -   c. where the or each spacer element for the second shell portion         is separate to this prior to assembly;     -   d. and wherein at least the second shell portion comprises an         aperture extending therethrough between the inner side and the         outer side thereof, via which the or each spacer element for         this portion can be secured thereto after the shell portions are         joined;     -   e. the lost formwork assembly further comprising:     -   f. at least one brace element of sufficient length to bridge         opposing inner sides of the two shell portions; and     -   g. a column reinforcement framework; and     -   h. the method of assembly comprising the steps of:     -   i. nesting the reinforcement framework in the first of the shell         portions so that this is separated from the shell by the spacing         elements, inserting the or each bracing element through the         reinforcement framework and securing them, securing the second         shell portion to the first shell portion along the edges         thereof; and then securing the or each spacer element for the         second shell portion thereto via the or each of the apertures.

In one form, at least the second shell portion comprises a line of the through apertures spaced apart there along, via which the or each spacer element for this portion can be secured thereto.

In one form, at least the second shell portion comprises at least a pair of parallel lines of the through apertures spaced apart there along, via which a pair of parallel spacer elements for this portion can be secured thereto.

In one form, the first shell portion comprises at least one line of the through apertures spaced apart there along, via which the or each spacer element for this portion can be secured thereto.

In a further aspect, there is provided a lost column formwork shell portion comprising an elongate body comprising a generally u-shaped cross-section shape comprising a pair of lengthwise extending edges, an inner side and an outer side, at least one spacer element depending from the inner side of the shell portion and projecting inwardly.

In one form, the cross-section shape of the lost column formwork shell portion comprises three straight sides, a first side, and then a pair of parallel sides extending from the first side.

In one form, at least one spacer element depends from each of the three sides of the lost column formwork shell portion.

In one form then, two shell portions cooperatively form a rectilinear cross-sectional shape.

In one form, each spacer element comprises a generally u-shaped cross-sectional shape.

In one form, each spacer element is arranged with an opening to its u-shape directed inwardly.

In one form, each spacer comprises a length of parallel flange channel (PFC).

In one form, each spacer element is elongate and extends along the column formwork shell portion.

In one form, in an alternative, the spacer might comprise a pair of plates standing upright on a lengthwise extending edge thereof, and arranged in parallel to each other.

In one form then, the method for assembling the lost column formwork assembly comprises the further steps of locating each end of each bracing element in the opening of one of the spacer elements, and securing each end to its respective spacer element, and thus with respect to the respective shell portion in turn.

In one form, in an alternative, the cross-section shape of the lost column formwork shell portion comprises a semi-circle.

In one form then, two shell portions cooperatively form a circular cross-sectional shape.

In a further alternative, the cross-section shape comprises half of a polygon shape. This polygon shape might comprise any one of a triangle, a pentagon, a hexagon, a heptagon, an octagon and so on.

In a further aspect, there is provided a lost column formwork shell assembly comprising:

a first shell portion and a second shell portion, each shell portion comprising an elongate body comprising a pair of lengthwise extending edges, and an inner side and an outer side, wherein at least a first shell portion comprises a generally u-shaped cross-section, and the shell portions are adapted to cooperatively form a column shell by being joined along their lengthwise extending edges;

each shell portion further comprising at least one spacer element depending from an inner side of each shell portion and projecting inwardly; and

wherein at least the second shell portion comprises at least one aperture extending therethrough between the inner side and the outer side thereof, via which the spacer element for this portion can be secured thereto.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the present disclosure will be discussed with reference to the accompanying drawings wherein:

FIG. 1 is a perspective view of a first shell portion for a lost column formwork assembly according to a first embodiment;

FIG. 2 is a perspective view of a second shell portion for use with the first shell portion of FIG. 1;

FIG. 3 is a perspective view of a spacer element for use with the first shell portion of FIG. 1 and the second shell portion of FIG. 2;

FIG. 4 is a perspective view of the lost column formwork assembly according to the first embodiment, comprising the elements illustrated in FIGS. 1 through 3, but minus a column reinforcement framework, which is omitted to permit visibility of other elements;

FIG. 5 is an end view of the lost column formwork assembly according to the first embodiment;

FIG. 6 is a perspective view of a first shell portion for a lost column formwork assembly according to a second embodiment;

FIG. 7 is a perspective view of a second shell portion for use with the first shell portion of FIG. 5;

FIGS. 8 and 10 are perspective views of the lost column formwork assembly according to the second embodiment, minus the second shell portion of FIG. 6 and a column reinforcement framework, which are omitted to permit visibility of other elements;

FIGS. 9 and 11 are perspective views of the lost column formwork assembly according to the second embodiment, minus the column reinforcement framework, which is omitted to permit visibility of other elements;

FIG. 12 is a detail view of an end of the first shell portion according to the second embodiment;

FIG. 13 is an end view of a lost column formwork assembly according to a third embodiment;

FIG. 14 is an end view of a lost column formwork assembly according to a fourth embodiment;

FIG. 15 is an end view of a lost column formwork assembly according to a fifth embodiment.

In the following description, like reference characters designate like or corresponding parts throughout the figures.

DESCRIPTION OF EMBODIMENTS

Referring now to FIG. 1, where there is illustrated a first shell portion 10 of a lost column formwork assembly 100 according to a first embodiment.

FIG. 2 illustrates a second shell portion 20 for use with the first shell portion 10.

The first shell portion 10 comprises an elongate body comprising a pair of lengthwise extending edges E, a generally u-shaped cross-section, and an inner side (within the u-shape) and an outer side.

The u-shape cross-section shape of the first shell portion 10 comprises three straight sides, a first side 12, and then a pair of parallel sides 14 extending from the first side 12. In this embodiment, each of these sides 12 and 14 is comprised of a mild steel plate, and these plates are welded together along their common edges.

At least one spacer element 30 depends from (in this case they are welded to) each of the three sides 12 and 14 of the first shell portion 10. Each of these spacers 30 comprises a length of mild steel parallel flange channel (PFC) comprising a generally u-shaped cross-sectional shape and oriented with an opening to this u-shape directed inwardly.

Each spacer element 30 is elongate and extends along the column formwork shell portion 10.

The spacer element 30 depending from the first side 12 of the first shell portion 10 and extends along a centreline thereof. The spacer elements 30 depending from each of the pair of parallel sides 14 extend along and beyond the edges E of the first shell portion 10.

Like the first shell portion 10, the second shell portion 20 comprises an elongate body comprising a pair of lengthwise extending edges E, a generally u-shaped cross-section, and an inner side (within the u-shape) and an outer side.

The u-shape cross-section shape of the second shell portion 20 also comprises three straight sides, a first side 22, and then a pair of parallel sides 24 extending from the first side 22. Again, in this embodiment, each of these sides 22 and 24 is comprised of a mild steel plate, and these plates are welded together along their common edges.

In this embodiment, the parallel sides 14 of the first shell portion 10 are approximately the same length as the parallel sides 24 of the second shell portion 20.

The first side 22 of the second shell portion 20 comprises a line of through apertures 26 spaced apart there along. The purpose of these apertures 26 relates to the separate spacer element 30 illustrated in FIG. 3, which will be explained further below.

Spacer element 30 of FIG. 3 is identical to those depending from the first shell portion 10, but is initially separate from the first shell portion 10, and assembled with this as assembly of the lost column formwork assembly 100 progresses.

Assembly of lost column formwork assembly 100 commences by laying the first shell portion 10 down with its opening directed upwards. Laying this shell portion 10 down is not essential, but makes the process easier. The structural reinforcement framework 50 is laid in the first shell portion 10 so that this is separated from the shell by the spacing elements 30.

As can be seen in FIG. 5, the reinforcement framework 50 is comprised of a plurality of hoops or rings 52 of thick steel bar joined in a spaced apart fashion by a plurality of long lengths 54 of thick steel bar extending in the direction of elongation of the column. The long bars 54 intersect the hoops 52 at positions spaced apart around these, and these are welded to each other at these points of intersection. The long bars 52 may extend beyond the ends of the shell portions 10 and 20 depending on the requirements for securing these to floors above and below the column to be formed. In this embodiment, the reinforcement framework 50 further comprises a plurality of cross-ties 56, each extending from one side of the framework 50 to the other, and looping around the rods 54 at its ends to tie the sides of the hoop 52 together and prevent unwanted spreading thereof.

The spacing elements 30 (and specifically the flange width of these in this case) are selected to ensure that the required ‘axis distance’ is maintained between the shell portions 10 and 20 and the reinforcement framework 50 in the completed lost column formwork assembly 100, and ultimately the completed column of which this lost column formwork assembly 100 will form a part. By providing a pair of flanges as opposed to single point of contact, the spacing elements 30 ensure that the axis distance is maintained.

The spacing elements 30 also improve the strength and rigidity of the shell portions 10 and 20.

With reference to FIG. 4, it can be seen that a plurality of bracing elements 40A, in the form of thick steel bars, are inserted through gaps in the reinforcement framework 50 (not illustrated in FIG. 4) and laid in a spaced apart fashion extending between the spacer elements 30 at either side of the opening to the first shell portion 10, with the ends of the bracing elements 40A nested in the opening between the flanges of the spacing elements 30, and secured by welding at the opposing ends thereof to the spacer elements 30. This process is performed one bracing element 40A at a time, starting at one end of the assembly 100 and progressing there along.

A plurality of further bracing elements 40B are inserted through gaps in the reinforcement framework 50 and stood upright in a spaced apart fashion, with a lower end positioned in the opening between the flanges of the spacing elements 30, and secured by welding them at this bottom end to the spacer element 30. This process is performed one bracing element 40B at a time, starting at one end of the assembly 100 and progressing there along.

The loose spacer element 30 illustrated in FIG. 3 is then positioned over the upper ends of the upright bracing elements 40B with its opening directed inwardly (downwards in this case) and its flanges either side of the upper ends of the upright bracing elements 40B. The upper ends of the upright bracing elements 40B are then secured by welding to the spacer element 30.

The second shell portion 20 is then positioned against the first shell portion 10 so that respective edges E of the shell portions 10 and 20 meet. The two shell portions 10 and 20 are then joined along these edges E so that they cooperatively form a shell of rectilinear (square in this case) cross-sectional shape.

The upper spacer element 30 is then secured by welding to the upper shell portion 20 by welds applied at each of the apertures 26 to the back of the upper spacer element 30.

Additional welds can then be made between bracing elements 40A and 40B and the reinforcement framework 50, to ensure that there is no movement of reinforcement framework 50 relative to the remainder of the assembly 100.

This assembly process can be performed with the aid of a specially made jig, to ensure accuracy in the completed assembly 100.

When assembled, the bracing elements 40A and 40B improve the strength and rigidity of the lost column formwork assembly 100. Usefully, they will reinforce the assembly 100 against bulging when the assembly 100 is filled with concrete, ensuring dimensional accuracy of the completed column.

While use of steel and welding is discussed herein, it should be appreciated that the invention is not so limited, and that plastic composites and adhesives could be used in an alternative.

It will be appreciated that the lost column formwork assembly, and its constituent parts, can be scaled and numbered as required, to produce columns of varying sizes.

Referring now to FIG. 6, where there is illustrated a first shell portion 10A of a lost column formwork assembly 100A according to a further embodiment.

In FIG. 7 there is illustrated a second shell portion 20A for use with the first shell portion 10A.

In FIGS. 8 through 11 there is illustrated the lost column formwork assembly 100A according to the further embodiment. Those parts of the lost column formwork assembly 100A which are identical (or near-identical) to corresponding parts shown in the lost column formwork assembly 100 of FIGS. 1 through 4, will be denoted by the same reference numerals and will not be described again in detail.

In this embodiment, the lost column formwork assembly 100A is sized to form part of a larger column than is formwork assembly 100. The design of a lost column formwork assembly will vary depending on the shape and dimensions of the column, and the structural requirements of the column.

The parallel sides 14 of the first shell portion 10A are approximately double the length of the parallel sides 24 of the second shell portion 20A.

Each of the pair of parallel sides 14 of the first shell portion 10A comprises a pair of parallel, equi-spaced spacer elements 30 depending therefrom and extending therealong.

The second shell portion 20A comprises a pair of parallel, spaced apart rows of apertures 26 extending therealong. The method of assembly of lost column formwork assembly 100A is much the same as that for assembling lost column formwork assembly 100 described above. During assembly, post insertion of the bracing elements 40B, the separate spacing elements 30 are secured to the upper ends of each of these, the first shell portion WA and the second shell portion 20A are joined along their matching edges E, and then each spacer element 30 for the second shell portion 20A is secured thereto via welding in the apertures 26.

The assembled lost column formwork assembly 100A comprises a parallel pair of rows of spaced apart transverse bracing elements 40A extending therealong, and a parallel pair of rows of spaced apart transverse bracing elements 40A extending therealong.

With reference to FIG. 12, there is illustrated a detail view of an end of the second shell portion 20A, permitting visibility of a lifting lug plate 70 via which the second shell portion 20A, and ultimately the lost column formwork assembly 100A, can be hoisted for transport and final positioning on the building site.

FIGS. 13 through 15 each illustrate an additional embodiment of a lost column formwork assembly. Each of these is intended for use in forming a column of a different size. As before, those parts of the lost column formwork assemblies which are identical (or near-identical) to corresponding parts shown in the lost column formwork assembly 100 of FIGS. 1 through 4, will be denoted by the same reference numerals and will not be described again in detail.

In the embodiment of each of FIGS. 13 through 15, the reinforcement framework 50 comprises an outer hoop 52 of reinforcement bar, and inner hoops 52 a. The embodiments of FIGS. 13 and 14 comprise two inner hoops 52 a, and the embodiment of FIG. 15 comprises three inner hoops 52 a. The design of the reinforcement framework 50 will vary depending on the shape and dimensions of the column, and the structural requirements of the column.

The lost column formwork assembly according to the present disclosure ensures that the required axis distance is maintained across its length, is braced against bulging under the hydrostatic pressure of concrete filling, and is quicker and easier to assemble than commonly known alternatives.

Throughout the specification and the claims that follow, unless the context requires otherwise, the words “comprise” and “include” and variations such as “comprising” and “including” will be understood to imply the inclusion of a stated integer or group of integers, but not the exclusion of any other integer or group of integers.

The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement of any form of suggestion that such prior art forms part of the common general knowledge.

It will be appreciated by those skilled in the art that the invention is not restricted in its use to the particular application described. Neither is the present invention restricted in its preferred embodiment with regard to the particular elements and/or features described or depicted herein. It will be appreciated that the invention is not limited to the embodiment or embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the scope of the invention as set forth and defined by the following claims. 

1. A lost column formwork assembly comprising: a. a first shell portion and a second shell portion, each shell portion comprises an elongate body comprising a pair of lengthwise extending edges, and an inner side and an outer side, wherein at least a first shell portion comprises a generally u-shaped cross-section, and the shell portions are adapted to cooperatively form a column shell by being joined along their lengthwise extending edges; b. each shell portion further comprising at least one spacer element depending from an inner side of each shell portion and projecting inwardly; c. and wherein at least the second shell portion comprises an aperture extending therethrough between the inner side and the outer side thereof, via which the spacer element for this portion can be secured thereto; d. the lost formwork assembly further comprising: e. at least one brace element of sufficient length to bridge opposing inner sides of the two shell portions; and f. a column reinforcement framework; and g. wherein the two shell portions are joined along their lengthwise extending edges to form a column shell, with the column reinforcement framework extending lengthwise through the shell and separated from the shell by the spacing elements, and with the or each bracing element extending through the reinforcement framework and between opposing inner sides of the two shell portions, and secured at opposing ends thereof with respect to the inner sides of the two shell portions.
 2. The lost column formwork assembly of claim 1, wherein each shell portion comprises an elongate body comprising a generally u-shaped cross-section shape comprising a pair of lengthwise extending edges, and an inner side and an outer side, and adapted to cooperatively form a column shell by being joined along their lengthwise extending edges.
 3. The lost column formwork assembly of claim 1, further comprising a plurality of the brace elements arranged in parallel, extending transversely across the shell and spaced apart lengthwise therealong.
 4. The lost column formwork assembly of claim 1, wherein each spacer element comprises a generally u-shaped cross-sectional shape arranged with an opening to its u-shape directed inwardly and opposing another spacer element, and wherein each end of each bracing element is positioned in the opening of one of a pair of opposing spacer elements, and secured at each end to its respective spacer element, and thus with respect to the respective shell portion in turn.
 5. A method for assembling a lost column formwork assembly comprising: a. a first shell portion and a second shell portion, each shell portion comprises an elongate body comprising a pair of lengthwise extending edges, and an inner side and an outer side, wherein at least a first shell portion comprises a generally u-shaped cross-section, and the shell portions are adapted to cooperatively form a column shell by being joined along their lengthwise extending edges; b. each shell portion further comprising at least one spacer element depending from an inner side of each shell portion and projecting inwardly; c. where the or each spacer element for the second shell portion is separate to this prior to assembly; d. and wherein at least the second shell portion comprises an aperture extending therethrough between the inner side and the outer side thereof, via which the or each spacer element for this portion can be secured thereto after the shell portions are joined; e. the lost formwork assembly further comprising: f. at least one brace element of sufficient length to bridge opposing inner sides of the two shell portions; and g. a column reinforcement framework; and h. the method of assembly comprising the steps of: i. nesting the reinforcement framework in the first of the shell portions so that this is separated from the shell by the spacing elements, inserting the or each bracing element through the reinforcement framework and securing them, securing the second shell portion to the first shell portion along the edges thereof; and then securing the or each spacer element for the second shell portion thereto via the or each of the apertures.
 6. The method of claim 5, wherein each spacer element comprises a generally u-shaped cross-sectional shape, and each spacer element is arranged with an opening to its u-shape directed inwardly, the method then comprising the further steps of locating each end of each bracing element in the opening of one of a pair of opposing spacer elements, securing each end to its respective spacer element, securing the second shell portion to the first shell portion along the edges thereof, and then securing the or each spacer element for the second shell portion thereto via the or each of the apertures.
 7. A lost column formwork shell assembly comprising: a first shell portion and a second shell portion, each shell portion comprising an elongate body comprising a pair of lengthwise extending edges, and an inner side and an outer side, wherein at least a first shell portion comprises a generally u-shaped cross-section, and the shell portions are adapted to cooperatively form a column shell by being joined along their lengthwise extending edges; each shell portion further comprising at least one spacer element depending from an inner side of each shell portion and projecting inwardly; and wherein at least the second shell portion comprises at least one aperture extending therethrough between the inner side and the outer side thereof, via which the spacer element for this portion can be secured thereto.
 8. The lost column formwork shell assembly of claim 7, wherein at least the second shell portion comprises a line of the through apertures spaced apart there along, via which the spacer element for this portion can be secured thereto.
 9. The lost column formwork shell assembly of claim 7, wherein at least the second shell portion comprises at least a pair of parallel lines of the through apertures spaced apart there along, via which a pair of parallel spacer elements for this portion can be secured thereto.
 10. The lost column formwork shell assembly of claim 7, wherein first shell and second shell portion cooperatively form a column shell of rectilinear cross-section shape.
 11. The lost column formwork shell assembly of claim 7, wherein first shell and second shell portion cooperatively form a column shell of rounded cross-section shape.
 12. A lost column formwork shell portion comprising an elongate body comprising a generally u-shaped cross-section shape comprising a pair of lengthwise extending edges, an inner side and an outer side, and at least one spacer element depending from the inner side of the shell portion and projecting inwardly.
 13. The lost column formwork shell portion of claim 12, wherein this comprises three straight sides, a first side, and then a pair of parallel sides extending from the first side.
 14. The lost column formwork shell portion of claim 12, wherein at least one spacer element depends from each of the three sides of the lost column formwork shell portion.
 15. The lost column formwork shell portion of claim 12, wherein each spacer element comprises a generally u-shaped cross-sectional shape.
 16. The lost column formwork shell portion of claim 12, wherein each spacer element is arranged with an opening to its u-shape directed inwardly.
 17. The lost column formwork shell portion of claim 12, wherein each spacer element is elongate and extends along the column formwork shell portion.
 18. The lost column formwork shell portion of claim 17, wherein a side comprises two or more spacer elements, these are spaced apart and extend parallel to each other.
 19. The lost column formwork shell portion of claim 12, wherein in one form, each spacer comprises a length of parallel flange channel (PFC).
 20. The lost column formwork shell portion of claim 12, wherein the cross-section shape of the lost column formwork shell portion comprises a semi-circle. 